The 4-fluorosalicylic acid derivative of the present invention is a novel compound which has been unknown and which is not described in any literature. It has been also unknown that the 4-fluorosalicylic acid derivative can become a useful raw material for producing a 3-fluorophenol derivative useful as an intermediate for liquid crystal [refer to Japanese Patent Application Kokai (Laid-Open) No. 291899/1995 and Japanese Patent Application Kokai (Laid-Open) No. 10847/1995], recording material [refer to Japanese Patent Application Kokai (Laid-Open) No. 264587/1991], agricultural chemical [refer to Japanese Patent Application Kokai (Laid-Open) No. 345740/1994], medicine [refer to Japanese Patent Application Kokai (Laid-Open) No. 309837/1995], etc.
The objects of the present invention are to provide a novel 4-fluorosalicylic acid derivative which can be easily converted to a 3-fluorophenol derivative useful as mentioned above, and a process for producing the 4-fluorosalicylic acid derivative.
The present inventors made a study in order to achieve the above objects. As a result, the present inventors found out that a useful 3-fluorophenol derivative can be easily produced by decarboxylation of a 4-fluorosalicylic acid derivative and that the 4-fluorosalicylic acid derivative used as a raw material in the decarboxylation is a novel compound not described in any literature and is useful not only as an intermediate in production of the 3-fluorophenol derivative but also in production of liquid crystals, etc. The present invention has been completed based on the above finding.